1. Field of the Invention
The present invention relates to an apparatus for sensing the state in a passenger compartment of a vehicle, such as an occupant state or the like in the passenger compartment, which is applicable to an air bag occupant restraint system for a vehicle or the like.
2. Description of Related Art
An air bag occupant restraint system for vehicles is being equipped as standard equipment nowadays and a usage rate of an air bag for the front passenger's seat is increasing. For example, the air bag operates to dissipate the occupant's forward motion to be relatively slow relative to internal structure in the passenger compartment such as a handle, an instrumental panel, and the like and prevents the occupant from directly striking the internal structure, thereby preventing the occupant from being injured by a crash of the vehicle.
An air bag system uniformly inflates an air bag by a collision detection signal of a collisison sensor which detects a crash of a vehicle basically independently of the state or the physique of the occupant.
From the viewpoint of protecting the occupant, however, it is not always preferable for the vehicle having the air bag system to uniformly inflate the air bag in the event of a crash. That is, it may be preferable from the viewpoint of occupant protection that the air bag is not inflated in a certain range where the state and the physique of the occupant are specified. Also, it may be preferable to change an inflating speed of the air bag and inflate the air bag in a specific range where the state and physique of the occupant are different from those of the above case.
For an occupant in an improper state contrary to a proper state where the function of the air bag effectively works, for example, in a state where an infant does not sit down on the seat but stands between the instrument panel and the seat (child standing state), in a state where an occupant sits on the seat but does not fasten a seat belt, bends forward, and the occupant's head is close to the instrument panel or the like, it is necessary to operate the air bag in correspondence with the state of the occupant.
Since the air bag is a system to protect basically an occupant, namely, a human, a means for very accurately discriminating the type of occupant as a human is necessary. With respect to an air bag for the front passenger seat, in a crash of a vehicle, the air bag is uniformly inflated even when an object (luggage or the like) is put on the passenger seat or no occupant exists. This operation is meaningless from the viewpoint of the inherent object of the air bag. A problem of increase in repair fee for air bag replacement or the like also occurs. Consequently, it is necessary to specify the kind of occupant, e.g., human, small animal, or other object.